so small size and light weight are prior considerations?
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if 18650 then the light will be heavier, is that ok?
but the 18650 battery itself is 50gr alrealdy
wow the suggestion of headband/clip design is very helpful!! Thanks 
sounds great! but do need time to design it without pics, has sent to our engineer 
Do you mean brightness changing also for red light?
Is the weight of 18650 battery acceptable?
+1 Well said!
Yes.
No it isn’t, personally for me it’s too heavy, but an extension tube should be an option for those wanting longer runtimes.
For me the best format is 14500 when there is support also for Ni-Mh.
The advantage of run in dual fuel as personal choise and the safe of Ni-Mh
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You like this old story , dont ya?
Dont worry It was two CR123As in series… take a deep breath and… don’t put flashlights in mouth
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- Don’t put headlamp in mouth
I take note
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18650 weight is fine for me
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Same for me! If you want a decent amount of light for longer time it is only option. 21700 on other hand is too heavy for me.
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Yeah, 21700 headlights are too heavy for most people.
I’d like to eventually get a 21700 headlight and see if I can handle the weight. 
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Zebralight H600 has acceptable weight - and it’s 1x18650. On the other hand - ArmyTek Wizard is too heavy for my taste - also 1x18650. So, 18650 user friendly headlamp is doable, but most such headlamps are too heavy. Also cheap 1x18650 like H25S are light enough because of !@#$y aluminum used 
18350 + 18650 tube is a good idea 
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Hello BLF, this is my first post here.
I see how personal preferences differ wildly when it comes to flashlight design. So I tried to unify as much of them as possible into one design, with attention to what already exists on the market. However fulfilling all of them is probably impossible with just one model. Of course I am no expert in electronics, machinig, anything else or all the responsibilities around that, but I think I can still design something functional.
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Quick answer to Sofirn’s questions with my preferations. /
1: 18650-battery.
2: 4500K-5700K for white light, 610-640nm for red light.
3: Horizonzal T-shape.
4: Configure so that holding clamp grips beneath pocket clip. [ shown in pictures ]
5: Single emitter-units, no combined optics. [ shown in pictures ]
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Now the very complicated, annoyingly long answer /
Here’s one drawing of my prototype-design, I call it “Sofirn H45”:.
It is basically an upgraded version of the very versatile “Sofirn D25”, that me and my family accumulated like other people shopping bags. Not that it is flawless, but the simplicity of clipping it in and out of the headband is pretty much unique at this price point. This version would primarily add output-power to it, aswell as a second channel for red light or something else, improve the water-resistance to “IP68”, due to the USB-port being underneath the upper tailcap, and enable a tailcap-held pocket clip to be on and stay on the flashlight, while it is mounted to a headband, fully compatible with those from “D25”.
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Additional suggestions for Sofirn. /
LED’s: “Nichia 519A” is probably the most popular option, but I would also strongly consider the “Cree XP-G4”, possibly the domeless variant with 90CRI, as it is more efficient, yet still nice to look at, and throws much further with these small optics. There should be a 5700K-option, as it is bright and natural. Anyways, more options are always better !. For the second channel I would look towards “Cree XQ-E” as they offer so much color-options.
Optics: TIR.-Lenses are lightweight and present the best beam at 30-45° for working at arms lenght. But for those who desire maximum-throw plus spill, there could be a reflector to buy seperately. Enthusiasts could then split the two beams with different optics, as shown in the drawing.
UI.: “Andùril 2” if possible, preconfigured to channel-switching, should otherwise have ramping and instant access to moonlight and second channel via hold and click-hold commands from off.
Driver: The “H45”-concept is purposefully designed to house a buck-driver with flashing pads on a two-level-board that takes up more space. I understand, multichannel-buck-driver is not easy and drives up the costs aswell, so maybe it’s enough if only the main-channel get’s a buck-converter with at least 5A and the second one a linear regulator with about 1-2A. Of course, the cherry on the top would be a powerbank-feature, that perfectly justifies the efforts of installing waterproof USB-connectivity.
Housing: “H45”-concept made by milling from aluminum, at least 4-axis-CNC required. The front-plate is currently thought to be from stainless steel, but it could be replaced by a machined or molded plastic part for the sake of weightsaving. The two screw-on-tailcaps are identical and can be made from round-stock by lathe.
Headband: I am generally okay with the “D25”-headband, but it could use a few refinements. The plastic is too thin where the elastic band slides in, and if you elongate the wedge that holds the light at its angle, over the entire lenght, then it doesn’t wear out so soon.
A clamping headband that swivels into place like the Olight-one that @ebastler showed wouldn’t fit to this concept, but would still be a smart option especially for smaller headlamps, and it could fit previous models like the “HS10” or “SP40” aswell.
Modularity: I am fully with @AEDe, Flashlights, like really all technical devices should be easy to dissasemble, with all components accessible and replaceable with hand tools and a soldering-iron. I had to already retire three lights from Sofirn and Wurkkos prematurely, because of a broken switch or a loose wire, that I simply couldn’t reach and repair, because of a glued driver and a pressfitted switch-ring. That’s why I mostly bought from Convoy recently. Please Sofirn, make me come back !, just … screw everything !.
Price: I would comfortably pay 30-40USD for a light like this.
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Now a bit of solioquy-FAQ /
Why 18650-cells, not something smaller, more lightweight ?. /
I don’t know about the sports-people among you, because I am a lazy cyclist, but I consider an “D25” a small and lightweight headlamp. Sure it shall not wiggle around when running, but that I think should be solved with a more sturdy headband, not by making huge compormises to the lamp’s build quality and runtime, just to save a few grams. Also a short tube on a t-shaped light would be difficult to mount into that clip-in-headband or be of just minimal reduction in size. An 18350-battery could still be used with a dummy cell, if Sofirn makes one available.
Still, the need for a better headband for l-shaped lights is there.
Does low-level white light defeat the purpose of red light ?. /
Absolutely not. We live on the edge of a swampy nature reserve with many small lakes. And when I am there at night and dare to challenge nature with a white headlamp, I immediately get swarmed by so many mosquitos, right into my eyes and mouth, that any high-protein-snack would be completely redundant.
Red light on the other hand is beyond most insects vision and attracts nothing ( at least nothing animal ). I like the deep-red aswell and use it as bike-rearlight, with the “D25LR” strapped backwards to my head, but it doesn’t even have to be 660nm-deep-red. Anything from 1800K-extreme-warm-white over 610nm-orange to phosphor-converted red does the job while attaining more lumens and wider color perception.
Why not L-shaped ?. /
Mostly because balance would be bad, like on my “Wurkkos HD20”, but the heat disissipation is also easier with the emitters and thermal mass close to the center.
Why position the switch at the side, not at the upper end ?. /
For a button to not be pressed accidental, it should be flush with it’s ring and be heavy to press. Unfortunately it is arkward to do this with one hand on a headlamp, when the switch is at the top. With a sideswitch you have something to press your thumb against, and due to it being an angled flashlight, finding the button shouldn’t be a problem either, as the light slides into the hand the same way everytime.
Also the space at the top is already occupied by the USB-board.
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That’s it from me, I would love to hear feedback and improvements to this design, as it may require changes in emitter configuration or materials, and thanks a lot to Sofirn for the opportunity of being part in designing products, I wish all companies would to it like this !.
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It’s good to have you here, Lumenix!
I wonder why the BLF software doesn’t say this is your first post. 
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